Development - About the Data

Estimates presented here are based upon the latest information from the National Resources Inventory (NRI). The NRI is a longitudinal sample survey based upon scientific statistical principles and procedures. It is conducted by the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS), in cooperation with Iowa State University’s Center for Survey Statistics and Methodology.

These results are based upon the 2007 NRI, which provides nationally consistent data for the 25-year period 1982–2007. Current estimates cover the contiguous 48 States. Separate estimates also cover Hawaii, Alaska, and the Caribbean Area.

Release of NRI results is guided by NRCS policy and is in accordance with OMB and USDA Quality of Information Guidelines developed in 2001. NRCS is releasing NRI estimates only when they meet statistical standards and are scientifically credible in accordance with these policies; also, measures of statistical uncertainty are provided for all 2007 NRI estimates released to the public.

The findings on land development come from the NRI data category "Developed Land," which comprises large urban and built-up areas, small built-up areas, and rural transportation land. The NRI uses this classification to account for every acre of developed non-Federal land within the Nation. Every parcel of developed land is described by only one of these categories.

The NRI approach to conducting inventories facilitates examination of trends in rural and developed land uses over time because –

the same sample sites have been studied since 1982

the same data have been collected since 1982 [definitions and protocols have remained the same]

the inventory accounts for 100 percent of the surface area

quality assurance and statistical procedures are designed/developed to ensure that trend data are scientifically legitimate and unambiguous

it is easy to track lands as they go from one land-use category to another

Irrespective of the scale of analysis, margins of error must be considered. Margins of error (at the 95 percent confidence level) are presented for all NRI estimates. Note that estimates of change between two points in time will be less precise (relatively) than estimates for a single inventory year because the changes will be occurring on a smaller fraction of the landscape.